An increase in polyamine biosynthesis is usually associated with increased cellular proliferation, suggesting that altered control of ornithine decarboxylase (ODC) and/or S-adenosylmethionine decarboxylase (SAMD) may account for the abnormal growth patterns of malignant cells. To learn more about the differences between normal and transformed cells in this basic metabolic pathway, the regulation of polyamine biosynthesis will be studied in hamster and mouse embryo cells in culture. The synthesis and accumulation of the polyamines, putrescine, spermidine and spermine, will be compared in normal cells, cells exposed to chemical carcinogens, and malignantly transformed cells. The ODC and SAMD activities and the polyamine concentrations under different culture conditions will be determined for each cell type. The relationship between the induction of ODC and the phenomenon of tumor promotion will also be investigated in vitro. The elucidation of how this critical metabolic pathway is involved in the expression and maintenance of the neoplastic phenotype should lead to rational approaches to the chemotherapeutic control of malignancy.